Jazzmaster wiring questions

[reluctant-builder]

I found this image of what is said to be traditional Jazzmaster wiring.

I heard, secondhand, that Matt Brewster, of 30th Street Guitars in NYC, said one could clip off the superfluous lug of the volume pot instead of soldering it to the pot housing. Is that a good idea?

Let's say I've taken Cagey's advice to heart (which I pretty much have) and I don't want to solder any grounds to my pot housings. When it comes to grounding capacitors, how best would I accomplish this if I eschew grounding them to the pots? Do I just solder them to another ground wire? Like, potentially, taking the .033 cap's ground and soldering it to the lead pickup's ground and then soldering that to wherever ... be it a screw or the bridge, or what. Good idea? Stupid idea?

The diagram has five different colors of wire ... six, I suppose, if those ground wires are black. I understand that different color wire is for the sake of knowing what goes where, but if I have only three varieties of colored wire, say I contrived some method of discerning difference like taping creme or blue masking tape near either end of a color already used (so red is red, but red with blue ends is ... etc.). Sufficient disambiguity? Or not?

I notice, in the above diagram, the jack is missing a ground wire.

Below is an image of a Rothstein pre-wired JM assembly.

Since the jack has a ground wire, I assume it was erroneously omitted from the diagram.

Looks like he's got a Novak P-90 in the bridge, which has a yellow hot wire ... versus the neck pup's white hot wire, and the yellow wire connecting the rhythm circuit switch to the master volume. So, maybe this lends some credence to me using only three colors of wire.

 

[tfarny]

The method of ground I use now is to screw a pickguard or other small screw into the side of the control cavity and wire every ground to it, then run one wire from there to the output. Neat, visually easy to track, simple. I think it's called "star grounding" but then again I know nothing of real electronics. I'll post a pic once I get my new baby all wired up in the next few days.

 

[Patrick from Davis]

In that picture the pick guard has a brass or copper shield on it.  That is also ground.  So the input jack's ground is the metal that makes up the ring and where the nut is to secure it to the guard.  So the lug is unnecessary if the copper foil on the guard is also connected to ground because the jack will be in contact with this.
Patrick

 

[reluctant-builder]

In that picture the pick guard has a brass or copper shield on it.  That is also ground.

Ah, right. Good call. I completely disregarded the "brass shield" because it was not visually distinct in the diagram.

Regarding the picture of the Rothstein assembly ... how would one ground to the bridge? I don't see any spare wires with which to do that. Does that mean ground to the Jazzmaster bridge is unnecessary?

 

[tfarny]

In that picture the pick guard has a brass or copper shield on it.  That is also ground.

Ah, right. Good call. I completely disregarded the "brass shield" because it was not visually distinct in the diagram.

Regarding the picture of the Rothstein assembly ... how would one ground to the bridge? I don't see any spare wires with which to do that. Does that mean ground to the Jazzmaster bridge is unnecessary?

At least on tune o matic bridges, what you do is run a wire through a pre-drilled hole from the control cavity to one of the bridge posts, and that connects all the metal parts + strings into the ground. I assume Jmasters are the same. You do have to ground your strings (via a bridge ground).

 

[Patrick from Davis]

If you have the trem part of the Jazzmaster, you can solder a wire to the piece that adjusts the spring tension.  Otherwise Tfarny has the way to go.  You have a wire put in the bridge post socket hole that comes out in the control cavity though a hole drilled in there.  When the post is pressed in, it makes contact with the wire, and problem solved.  I thin there is a way to have the socket press the wire against the side of the hole, but I've never done it.  Never had to.
Patrick

 

[Cagey]

I heard, secondhand, that Matt Brewster, of 30th Street Guitars in NYC, said one could clip off the superfluous lug of the volume pot instead of soldering it to the pot housing. Is that a good idea?

In a word? No. He may have been talking about tone pots, and somebody got confused.

Volume pots are wired to be what's called a "voltage divider". A pot is basically a variably tapped resistor. You have a reference on one side (usually ground or common), the signal on the other, and the wiper taps off any point in between and becomes the new signal wire.

If you took off the reference point, the pot then becomes essentially a variable current limiter. This is next to useless in a guitar.

Let's say I've taken Cagey's advice to heart (which I pretty much have) and I don't want to solder any grounds to my pot housings. When it comes to grounding capacitors, how best would I accomplish this if I eschew grounding them to the pots? Do I just solder them to another ground wire? Like, potentially, taking the .033 cap's ground and soldering it to the lead pickup's ground and then soldering that to wherever ... be it a screw or the bridge, or what. Good idea? Stupid idea?

You need a ground point of some sort, and they can take a variety of forms. Depending on the guitar, some are easier to deal with than others. I prefer lugs that slip onto the pots themselves, as it kills two birds with one stone. See here...

That happens to be a tone pot, so I could cut one lug off. Also notice the short lead goes on the signal side, while the long lead is on the ground side. Less chance of picking up stray signal. Also, the lug grounds the pot housing, although these are open-back pots so it's not quite as effective as one might hope for.

The diagram has five different colors of wire ... six, I suppose, if those ground wires are black. I understand that different color wire is for the sake of knowing what goes where, but if I have only three varieties of colored wire, say I contrived some method of discerning difference like taping creme or blue masking tape near either end of a color already used (so red is red, but red with blue ends is ... etc.). Sufficient disambiguity? Or not?

That's up to you. You could wire the whole thing with one color if you wanted to. Electrically, it makes no difference whatsoever. For instance...

That's not as clean as it ended up being, and it's missing a ground wire, but you get the idea.

 

[reluctant-builder]

You need a ground point of some sort, and they can take a variety of forms. Depending on the guitar, some are easier to deal with than others. I prefer lugs that slip onto the pots themselves, as it kills two birds with one stone. See here...

That happens to be a tone pot, so I could cut one lug off. Also notice the short lead goes on the signal side, while the long lead is on the ground side. Less chance of picking up stray signal. Also, the lug grounds the pot housing, although these are open-back pots so it's not quite as effective as one might hope for.

Thanks, Cagey; that's an informative reply. The visuals are really helpful.

Since I have no solder lugs and, right now, don't want to buy anything else for this build -- particularly one item that will likely cost more to ship than to buy -- I intend to cut short one lead on the capacitor and solder it to the pot lug and then solder the longer lead (alligator clip between the solder point and the capacitor components) directly to a piece of copper wire that will go to ground. That seems satisfactory, based upon my understanding so far of how to wire a guitar. Whether it is actually satisfactory, though, is the question.

 

[Cagey]

Send me a PM with an address, and I'll see that you get some lugs.

 

[reluctant-builder]

Got the lugs today. Thanks, Cagey.

When my Warmoth delivery finally comes ... I'll see how well I can put them to use.  :icon_smile:

 

[Cagey]

You're welcome.

When you begin installation, you may want to grab the pointed end of that lug and bend it up on a bit of an angle (see first picture above), otherwise depending where it's going it may lay flat in the cavity and make it difficult to get wires/components in the little hole.

 

[reluctant-builder]

In honor of my Novak pickups arriving today (well, slated to arrive; I don't have them in-hand, yet), I'm posting an appropriately backwards image of the wiring for my "backwards" Jazzmaster.

With the Hagstrom Swede's rewiring under my belt (as arduous and sometimes frustrating as it was) and the great aural results of that experiment, I'm pretty confident about this new wiring challenge.

First things first, though. Hope some good assembly progress is made tonight so that wiring her up will be all that's left to do.

 

[stubhead]

The way I think of "ground" is it's just a drain. Water can run off anywhere, an an electrical "ground" is just a leakage off to... the Dead Zone. Active wiring is a lot different, because then you have voltages that can push back up through wires to dick around where they shouldn't....

If it goes very far past a simple one pickup-one volume circuit, I may do a written-language version first. I mean, sit down with a pen and paper and starting with the signal coming from one pickup, it then goes... to a selector switch, then master volume & tone? Or does each pickup have it's own set of controls, so you get like:

Pickup 1 -> volume 1 -> tone 1 (through capacitor back to) -> volume 1 ->
Pickup 2 -> volume 2 -> tone 2 (through capacitor back to) -> volume 2 ->    selector -> output jack

Wires inside a guitar ought to have a reason for their existence*, and this can help a bit.




*(as should we all, but that might take another diagram) :icon_tongue:

 

[reluctant-builder]

Check my in-progress thread for the unveiling of my Novak pickups; http://www.unofficialwarmoth.com/index.php?topic=17778  :icon_biggrin: